A novel and facile route which was a combination of sol–gel and hydrothermal processes to prepare single pure phase rutile VO2 nanopowder had been developed. V2O5 _ nH2O sols were prepared by the dissolution reaction of V2O5 in H2O2. Using these precursors, VO2 powder with the average size less than20nm and narrow size distribution was obtained by pre-reduction and hydrothermal treatment with careful control of the molar ratio of V2O5 to N2H4. The as-prepared powders showed excellent optical properties. The coated films reached a sufficiently high luminous transmittance (45–60%) and keeping the thermochromic effect in the infrared area very well. VO2 powders with such high quality had not been reported until now and its optical properties are comparable with high quality single layer VO2 film deposited by PVD. The as-prepared nanopowder has a phase transition temperature (tc) about 55.5 C and it can be tuned down to ambient by slight tungsten doping without deteriorating the thermochromic properties. DSC measurement disclosed that the tc reduction efficiency of tungsten was about -21.96 K/at.%w in the doping range from 0 to 2.5 at.%w. The basic reason for the formation of VO2 with different morphologies in acid and alkali conditions was contributed to variety of vanadium species which depend mainly on vanadium concentration and pH